Automatic wear take-up mechanism for internal expanding hydraulic brakes



Aug. 18, 1953 J. A. sHlPEs 2,649,168

AUTOMATIC WEAR TAKE-UP MECHANISM F OR INTERNAL EXPANDING HYDRAULIC BRAKES Filed Sept. 11. 1950 2 Sheets-Sheet 1 Fig.

Fig. 2

John A. Shipes l l2 INVENTUR.

Aug. 18, 1953 J. A. sHlPEs 2,649,168

AUTOMATIC WEAR TAKE-UP MECHANISM FOR INTERNAL EXPANDING HYDRAULIC BRAKES Filed sept. 11, 195o :esmas-sheet 2 y l m""""""\ Q INVENToR.

9 BY @n Z2 d..

aou/#mmf MQMS Patented Aug. 18, 1953 AUTOMATIC TAKEJUP 'MECHANISM FOR INTERNAL EXPANDING HYDRAULIC BRAKES John A. Snipes, charlotte, N.:o. I t

Application September 11, 1950, Serial N o. 184,268

5 .Claims.

My invention relates vto improvements in automatic :wear take-up mechanism for internal expanding shoe type hydraulic brakes, of automobiles especially, although not necessarily.

The primary -object of my invention is to prozvide in such brakes improved yratchet bar ,mechanism v automatically operative to take up wear on the brakeshoes as an incident to engagement of the bralieshoes with the brake drum `so as to :maintain a uniform predetermined brake -clearrance when the brakeshoes are disengaged, and which iis more efficient :than similar mechanisms, :simplein construction, easy to install and. inexfpensive to manuiacture=-and service.

Other and subordinate objects, within the purview of my invention, together with the pre- .cise nature of my .improvements will be readily :understood when the succeeding description and .claims are read with reference tothe drawings :accompanyingiand forming part of .this speciication.

In said drawings:

Figure 1 is -a view :inside 4elevation, fpartly in longitudinal section, of an internal expanding shoe-type hydraulic brake :structure embodying .my improved wear takeup mechanism, the .position of .the parts :being villustrated :as vwhen the brakeshoes are disengaged and 4without c wear on the same;

Figurez2 is :a fragmentary enlarged 4iview'iof the lsame.illustrating the position-of the zparts when the brakeshoes are engaged;

iFigurezS :is a yietvfsim'ilar torFigure .2 :illustrating the `manner iin which my :improved imechanism takes up wear as an .incident to ,engage- -ment -fof `the brakeshoes;

Figure .4 is.a similar view .illustrating lthe 'positionpf :the parts when the :brakeshoes are disengaged after .a .wear ftake-upoperation;

Figure 5 is another .similar f view .illustrating the :wear take-up Amechanism disconnected :preparatory to presetting the same for a..desired fclearance;

lEigure .6 fis a detail enlarged .view in vertical ,section a takenzon .the :line .i6-f6 :.of. .-l=igure'' .'Fligure ..7 fis Lan Yenlarged. yievv iin longitudinal `section-oi :the fhydraulic .brakenylinder;

:Figure 8 .is an enlarged :View ein iperspective 'f of .the .'longer, :upper ratchet:bar; tand .Figure A9 is asimilar '.viewofithe Llovver, shorter 'ratchet bar.

Referring-.to the :drawings by numerals,:l desiignates the :conventional :internalexpanding .shoe .type hydraulic lorakeastructure of ran iauto mobile, :not shown, :and including ;.the usual irotary brake .drum .2, :the brakeshoes 3, lined, :as

atari, ;andpivoted,;asfat .5,:on a mounting `Ii, bolted l.as vat 1, .to the usual fixed back, shoe carrying plate `8. The brakeshoes 3 are expanded `in the usual manner by swinging the Asame into engagement with the brake drum i2 by hydraulic pressure in a brake cylinder 9 voperating against .the pistons vIl) to separate thesame, -the pistons I0 having plungers I -I provided Wit-11.g-rooved heads I2 straddling the free ends I3 of lthe brakeshoes;3.

The numeral I 4 designates the conventional brake releasing spring Connected `to Said shoes 3, .as at .I 5, I6, to retractsaid'shoes into 'brake .disengaging position.

According to my invention, rratchet bar mecha- Vmsm is provided for automatically taking up vbrake wear comprising an upper, relatively long, horizontal :ratchet bar Il A carried by and -pivoted lat .one.end, as at It, to one brakeshoe 3 4'for vertical swinging .moi/ement in overlapping adja- '.able yfor a purpose presentlyseen A longitu- .dinal hollow guidesleeve; 2l ofrectangular form .-in cross-section-.dependsfromsaid ratchet ybar IjI .below the row ,of teeth y11.9 and is formed nte- .grally-witnsaidhar I 'I withits-bottom 21133121181 with said rowof teeth ,1:I 9.an d a flieht 'endflongitudinal vslot 23 in said sleeve belowsa-id :row of vteeth .-Iior a .purpose presently seen. `*Iherow of teeth le lextends along .the .top of the slot and through the topof thesleeve'with the teethgcollntersunkin said bar J1. A :Ufshaped springgd is with itsend .suitablyccnnected .to said .ratchet bar .I7, .as at 25,andfto `the brakeshoe as at :.25, :carryingsaid bar lvl, so as to tensionsaid hariand lurge the .same downwardly. lThe v.ratchet bar Il?, `ratchetteeth laand guide sleeve ;2I may be -castin one piece or otherwise suitably affirmed.

A lower, relatively .shorter tratchet bar 21 is lcarried ,by .the other brakeshoe .lexbeneath said' ratchet bar Il and in the sleeve 2| and is piuoted 'adjacent'one end, .as at 2-8, on said other 'brakeshoe Y3 vforvertical swinging 'in vsaid sleeve .with :upper edge ratchet'teeth :29 complementing :the :row-of ratchet-.teeth I9 for interlocking engage- '.menttherewith, .as shown in Figure .1, .to prevent retraction of Vthe brakeshoes ;3 into .brake .disengaging -position beyond a selected Ldegree of ybrake clearance provided as presently described.

3 engaged, after predetermined clearance, the upper ratchet bar I1 under the tension of the spring 24 tends to bear downwardly against one end tooth 29 on one side of the pivot 28 of said ratchet bar 21, thereby swinging said ratchet bar 21 upwardly on the other side of its pivot into substantially parallel relation to the upper ratchet bar I1 so that all of the teethY 29 on said 'lower ratchet bar 21 engage teeth I9 on the upper ratchet bar I1 in interlocking engagement therewith to maintain the brake clearance. As will be clear, the ratchet bars I1, 21 areendwise adjustable longitudinally, relatively,l upon engaging movement oi the brakeshoes 3. However, upon such endwise movement of said ratchet bars I1, 21, the ratchet bar 21, by frictional engagement of the ratchet teeth I9 with said end tooth 29 on the lower ratchet bar 21, swings the lower ratchet bar 21 downwardly, as shown in Figure 2,

into inclined position so that said end tooth 29,

only, is positioned to interlock with teeth I9. This swinging movement of the lower ratchet bar 21 compensates for longitudinal adjustment of said ratchet bars, relatively, during engaging movement of the brakeshoes 3 and is limited by the bottom 22 of sleeve 2 I.

Means are provided for swinging the upper ratchet bar I1 clear of the lower ratchet bar 21 into tooth disengaging position comprising the following:

A wrench hold member 35 is fixed on the outer end of a rock shaft 36 extending through the back plate 8 into the brake drum 2 and journaled in said plate 8 beneath the sleeve 22. A crank 31 is Iixed on the inner end of said rock shaft 36 inside the brake drum 2 for upward swinging by rocking of said rock shaft 36 in one direction whereby to engage and swing upwardly a lever 33 pivoted, as at 39, on the brakeshoe sleeve carrying the lower ratchet bar 21. Upward swinging of the lever 38 engages a lateral pin 39 thereon with the bottom 22 or" the sleeve 2i to swing the upper ratchet bar I1 upwardly and disengage the ratchet teeth I9 from the ratchet teeth 29.

`Such movement of the upper ratchet bar l1 engages the bottom 22 of the sleeve 2l with the lower ratchet bar 21 and swings said bar 21 into horizontal position, all as shown in Figure 5. `A stop 49 on the brakeshoe 3 on which the lever 38 is pivoted limits downward swinging of said lever 38,1and another stop liI on said brakeshoe 3 limits downward swinging of the crank 31. A suitably arranged coil spring 12 on the rock shaft 36 normally rocks said rock shaft in a direction to swing lthe crank 31 downwardly against its stop 31.

After the ratchet bar mechanism is disengaged, as above described, and with the brakeshoes 3 disengaged, the upper ratchet bar I1 may be lowered from its upswung position to engage its ratchet teeth I9 with the ratchet teeth 23 with the beforementioned end tooth 29 engaging a selected ratchet tooth I9, whereby to predetermine the degree of brake clearance with the new brake lining 4, as shown in Fig. l. The slot 23 provides for using a tool on bar 21 in this operation.

Referring now to the operation of my invention as so far described, with the brake clearance predetermined for a new brake lining in the manner above described, engaging movement of the brakeshoes 3 will cause the upper ratchet bar I1 to move endwise relative to the lower ratchet bar 21 to swing said bar 21 into the described inclined position with one end tooth 29 engaged -wth one tooth I9 of the upper ratchet bar I1.

4 Now, when the brakeshoes 3 are disengaged, and the lining 4 not worn, the lower ratchet bar 21 will be swung into parallel relation to the upper ratchet bar I1, in the manner previously described, to interlock the ratchet teeth I9 and 20 and maintain the predetermined brake clearance, as will be clear. However, as soon as the brake lining 4 wears in degree igreater than the spacing between the ratchet Vteeth I9, 29, the upper and lower ratchet bars I1, 21, as an incident to engaging movement of the brakeshces 3, will be moved longitudinally endwise, relatively, so that the ,tooth I9 engaging the end tooth 29 on the lower ratchet bar 21 will ratchet over said end toothrand position a succeeding tooth I9 into engagement with said end tooth 29, all as shown in Figure 3. This will cause longitudinal adjustment of the ratchet bars I1, 21 in correspondence` with the degree of lining wear to take up such wear and so that retraction of the brakeshoes 3 into brake disengaging position will be limited in correspondence with the degree of wear to maintain the predetermined brake clearance. This relative longitudinal adjustment of the ratchet bars I1, 21 will occur each time a sumcient degree of wear has occurred on the brake linings il, and, as will be clear, the ratchet teeth I9, 29 may be spaced to take up as little as fourthousandths of an inch of wear at a time.

It is to be noted that the degree of brake clearance established by the described operation of the ratchet bars I1, 2| may be varied, that is, increased, or diminished, by varying the degree of downward swinging movement of the lower ratchet bar 2'?, as by using upper ratchet bars I1 having sleeves 2| of different depths internally to variably limit downward swinging of said bar 21. Thus, with the proper spacing between ratchet teeth I9, 29, the mechanism may be preset for brake clearanceA of such slight degree as twenty-five thousandths of an inch.

In addition to the foregoing, the hydraulic cylinder 9 is rendered dust proof, as follows. The plungers II are threaded into sockets 45 in the pistons I0 and slidably extend through dust caps 46 iitted over the ends of the cylinder S. Coil springs 41 on the plungers I I, between said caps and the grooved heads I2, maintain said caps 46 tight against the ends of said cylinder 9. The numeral 48 designates the conventional cushioned spring between the pistons I0, which need merely be identied in passing.

The foregoing will, it is believed, suffice to impart a clear understanding of my invention, without further explanation.

Manifestly, the invention, as described, is susceptible of modification without departing from the inventive concept, and right is herein reserved to such modifications as fall within the scope of the appended claims.

Having described the invention, what is claimed as new is:

1. An internal expanding brake comprising a pair of pivoted brakeshoes movable into brake engaging `and disengaging positions, respectively, a pair of relatively long and short ratchet toothed bars each pivoted adjacent oneend on an asso- ,ciatedbrakeshoe for swinging movement thereon with the ratchet teeth of said bars facing, spring means pressing the longer bar against the shorter bar to normally swing said shorter bar parallel with the longer bar for interlocking of the teeth of said bars when said shoes are disengaged to limit disengaging movement of said shoes and establish the degree of brake clear.-

ance, said bars being longitudinally adjustable oppositely by engaging movement of said shoes and with a tooth of the longer bar frictionally engaging one tooth of the shorter bar at one side of its pivot to swing said shorter bar in one direction, such swinging of said shorter bar compensating for longitudinal adjustment of said bars with said one tooth interlocked with teeth of the longer bar, means limiting such swinging of said shorter bar to cause the longer bar to ratchet over said one tooth and automatically vary the position of said bars longitudinally whereby to take up wear on the shoes when said shoes are disengaged, and means to swing said longer bar clear of said shorter bar into tooth disengaging position for manual setting to engage said teeth in different longitudinal positions of said bars for predetermining the brake clearance.

2. An internal expanding brake according to claim 1 wherein said second-named means comprises a stop member on said longer bar engaged by said shorter bar.

3. An internal expanding brake according to claim 1 wherein said second named means comprises a longitudinal sleeve on said longer bar in which said shorter bar swings into engagement therewith.

4. An internal expanding brake according to claim 1 said last-named means comprising a rock shaft and a crank on said shaft, and a pivoted lever operative by said crank for swinging said upper bar.

5. An internal expanding brake comprising a pair of pivoted brakeshoes movable into brake engaging and disengaging positions, respectively, a pair of relatively long and short ratchet toothed bars each pivoted adjacent one end on an associated brakeshoe for swinging movement thereon with the ratchet teeth of said bars facing, spring means pressing the longer bar against the shorter bar to normally swing said shorter bar parallel with the longer bar for interlocking of the teeth of said bars when said shoes are disengaged to limit disengaging movement of said shoes and establish the degree of brake clearance, said bars being longitudinally adjustable oppositely by engaging movement of said shoes and with a tooth of the longer bar frictionally engaging one tooth of the shorter bar at one side of its pivot to swing said shorter bar compensating for longitudinal adjustment of said bars with said one tooth interlocked with teeth of the longer bar, means limiting such swinging of said shorter bar to cause the longer bar to ratchet over said one tooth and automatically vary the position of said bars longitudinally whereby to take up wear on the shoes when said shoes are disengaged.

JOHN A. SHIPES.

References cited in the fue of this patent UNTTED STATES PATENTS Number Name Date 2,087,196 Tarbox July 13, 1937 2,303,699 Main Dec. 1, 1942 2,322,492 Williams 'June 22, 1943 2,522,181 Krikorian Sept. 12, 1950 

